Dishwasher with a fresh water tank

ABSTRACT

The present invention relates to a dishwasher, in particular a domestic dishwasher, having a control device in which one or more wash programs for controlling a wash cycle for washing items to be washed can be called, and having a fresh water inlet device for receiving fresh water from an external cold water supply, wherein a fresh water reservoir which can be filled with fresh water by means of the fresh water inlet device is provided in which a volume of fresh water can be stored that is sufficient to cover the fresh water requirements of a wash cycle in the case of at least one of the wash programs.

BACKGROUND OF THE INVENTION

The present invention relates to a dishwasher, in particular a domestic dishwasher, having a control device in which one or more wash programs can be called for the purpose of controlling a wash cycle for washing items to be washed, and having a fresh water inlet device for receiving fresh water from an external cold water supply.

In the case of known domestic dishwashers the dishes to be washed are cleaned automatically in a washing process, also referred to as a wash cycle, with the aid of washing water in accordance with a wash program. For that purpose a plurality of wash programs are usually stored in a control device, of which programs one is called each time and used to control the wash cycle. Selecting and starting a wash program is generally a task performed by an operator, but can also be initiated automatically by means of a control device. The further execution sequence of a wash cycle is then controlled automatically by means of the control device. In this case a wash program typically provides a plurality of wash subcycles succeeding one another, wherein the washing water is provided with cleaning agents and/or additives as a function of the execution of the respective wash program and brought to a temperature that is favorable for the respective wash subcycle.

In order to cover the water requirements for performance of a wash cycle, known dishwashers have a fresh water inlet device for receiving fresh water. Fresh water inlet devices of said kind are provided for the purpose of being connected to an external fresh water supply which provides fresh water that is under pressure. In this scenario the supply can consist of a water pipe installed in the building. Whereas in the American region there is a predominance of dishwashers of the type that are provided for connection to an external hot water supply, in Europe the most common types of dishwasher are those which are designed to be connected to an external cold water supply.

A typical wash cycle in the case of a domestic dishwasher of European type includes in particular, in this chronological order, a prewash cycle, a cleaning cycle, an intermediate wash cycle, a rinse cycle and a drying cycle.

After the start of a wash program the prewash cycle is started, wherein firstly fresh water is introduced from the external cold water supply into the washing compartment of the dishwasher by means of a corresponding activation of the fresh water inlet device. By means of a corresponding activation of a circulating pump the fresh water is then circulated as washing water in order thereby to remove coarse dirt from the items to be washed. Usually the washing water of the prewash cycle is not heated. After a predefined time at least a part of the now dirty washing water is then pumped out through appropriate control of a drain pump and the prewash cycle is terminated.

At the beginning of the now following cleaning cycle, further fresh water from the external cold water supply is introduced into the washing compartment by repeated control of the fresh water inlet device. This water is heated by activating the heating device in a heating phase of the cleaning cycle. During the heating phase of the cleaning cycle detergent is usually added to the washing water now contained in the washing compartment by way of a detergent dispensing device controlled by the control device. Furthermore, during the heating phase of the cleaning cycle the circulating pump is controlled in such a way that the washing water is circulated in order thus to enable stubborn dirt also to be removed from the items to be washed. When the temperature of the wash cycle reaches a value predefined by the wash program, this is detected by means of the sensor for the temperature of the wash cycle, whereupon the control device switches off the heating device. Following the now completed heating phase of the cleaning cycle a post-cleaning phase or post-washing phase of the cleaning cycle with a predefined duration is performed during which the washing water continues to be circulated. At the end of the post-washing phase the drain pump is activated once again, with the result that at least a part of the washing water of the cleaning cycle is pumped out.

At the beginning of the now following intermediate wash cycle, the washing water in the washing compartment is topped up again by way of the fresh water receiving device. Usually the washing water of the intermediate wash cycle is not heated, though it is circulated by means of the circulating pump. In particular detergent residues can be removed from the items to be washed by means of the intermediate wash cycle. After a predefined period of time has elapsed the washing water of the intermediate wash cycle now including detergent residues is at least partially pumped out.

At the beginning of the following rinse cycle the fresh water inlet device is once again activated in order to introduce fresh water into the washing compartment. This water has rinse aid added to it by means of a rinse aid dispensing device, is heated by activation of the heating device and circulated by means of corresponding activation of the circulating pump. When a designated temperature is reached the circulating pump and the heating device are switched off. In addition the washing water is pumped out by way of the drain pump and the rinse cycle terminated. The rinse cycle serves in particular to avoid spotting on the cleaned items to be washed, which is essentially achieved by means of the chemical properties of the rinse aid. The rinse cycle also serves generally for preparing the items to be washed for the now following drying cycle by bringing said items to a relatively high temperature.

During the now following drying cycle, in which no new washing water is introduced into the washing compartment, the washing water still adhering to the items to be washed evaporates owing to the high temperature of said items by means of what is termed “sensible heat convection”. This water then condenses mostly on the walls of the washing compartment and collects in a lower region of the washing compartment. From there the washing water is pumped out after a predetermined time by means of the drain pump and the drying cycle is terminated.

The described basic execution sequence of a typical wash cycle can be modified in diverse ways. Thus, for example, different time constants or different temperatures can be specified. It is also possible to omit individual wash subcycles, such as, for example, the prewash cycle and/or intermediate wash cycle, or to perform individual wash subcycles, such as, for example, the cleaning cycle, several times in succession. In this way it is possible to adapt the provided execution sequence of the wash cycle to different application situations.

The selection of a suitable wash program can considerably improve the efficiency of the cleaning of items to be washed under certain conditions. In this case the efficiency corresponds to the ratio of the washing result achieved by means of a wash cycle and the resources necessary therefor, i.e. for example the energy required, the water required and/or the time required for the respective wash cycle.

Against the background of increased energy and water costs, but also against the background of increased environmental awareness as well as changes in lifestyle of wide sections of the population, a need has developed for more efficient domestic dishwashers.

A disadvantage in the case of the known dishwashers is that these no longer come up to today's demand for efficiency.

BRIEF SUMMARY OF THE INVENTION

The object of the present invention is to provide a dishwasher, in particular a domestic dishwasher, having a higher level of efficiency.

This object is achieved in the case of a dishwasher, in particular a domestic dishwasher, of the type cited in the introduction in that a fresh water reservoir which can be filled with fresh water by means of the fresh water inlet device is provided in which a volume of fresh water can be stored that is sufficient to cover the fresh water requirements of a wash cycle in the case of at least one of the wash programs.

The temperature of a typical household cold water source such as e.g. a cold water pipe is usually less than an ambient temperature in which a dishwasher is operated. By means of the fresh water reservoir it is possible to introduce the fresh water required for a wash cycle from the cold water supply into the fresh water reservoir and to store it there before it is taken out of the fresh water tank again for the purpose of performing the wash cycle. During this time that it resides in the fresh water reservoir the fresh water can be heated by heat absorption from the environment to a usage temperature which is higher than its original supply temperature when fed into the fresh water reservoir. In particular the fresh water introduced into the fresh water reservoir can heat up to ambient temperature if it has spent a sufficiently long time residing in the fresh water reservoir. Thus, for example, it is at the ambient temperature if after execution of a wash program on the previous day it is taken from the fresh water reservoir on the following day for the wash subcycles of a freshly started wash program. In this way preheated fresh water is available for the wash cycle of the selected wash program in each case, which fresh water can be brought from its original supply temperature to a higher working temperature without additional auxiliary heating already just through utilization of the ambient heat in the room in which the dishwasher is installed. In the ideal case, therefore, the preheated fresh water has a temperature which corresponds to the ambient or room temperature. This can be, for example, 8° C. to 10° C. above the temperature of the cold water supply.

The storage capacity of the fresh water reservoir is dimensioned such that the amount of fresh water that can be stored in the fresh water reservoir at least covers the water requirements envisioned by one of the stored wash programs for a full wash cycle. This wash program can advantageously be brought to the attention of an operator as particularly energy-efficient e.g. by means of an extra economy button or energy efficiency button and/or a display. In this way it is ensured that preheated fresh water can be held in reserve for each fresh-water-consuming wash subcycle of the wash cycle.

For unheated water-conducting wash subcycles of the wash cycle controlled in accordance with the respective wash program this results in a higher washing temperature, thereby increasing its cleaning effect while the energy requirement effectively remains the same. In the case of heated water-conducting wash subcycles the result is an energy saving, based on the fact that with the preheated fresh water less heat needs to be supplied in order to reach the designated washing temperature.

The higher average temperature during a wash cycle with water that is preheated, in particular due to the ambient heat alone, also results in a higher thermal cleaning effect. This means that in many cases it is possible to shorten the designated running time of a wash program, which can lead not only to a time saving, but also to a further energy saving on account of a shorter operating time of the circulating pump.

All in all, the dishwasher according to the invention enables more efficient operation for at least one wash program.

According to a preferred development of the invention an amount of fresh water sufficient to cover the fresh water requirements of a wash cycle in the case of a plurality of the wash programs can be stored in the fresh water reservoir. In this case the advantages according to the invention can be realized for a plurality of wash programs. This permits a wash program suitable for the particular application situation to be selected from a plurality of efficiently executable wash programs.

According a particularly preferred development of the invention an amount of fresh water sufficient to cover the fresh water requirements of a wash cycle for each of the wash programs can be stored in the fresh water reservoir. In this case it is ensured that each of the provided wash programs can be performed in an efficient manner.

According to a beneficial development of the invention at least 8 liters, preferably at least 12 liters, and particularly preferably at least 16 liters of fresh water can be stored in the fresh water reservoir. With such a dimensioning of the fresh water tank a significant increase in the efficiency of the dishwasher can be achieved.

According to an advantageous development of the invention the fresh water reservoir is disposed externally on at least one wall, in particular a sidewall, of the washing compartment of the dishwasher. This enables the dishwasher to be shipped and operated as a compact structural unit with integrated fresh water reservoir. In particular the fresh water reservoir can beneficially be provided in the interspace between an outer housing, if this is present, and at least one wall, in particular a sidewall, of the internally disposed washing compartment of the dishwasher and therefore inside a housing. In this way damage-prone, external, electrical and/or hydraulic connections between the fresh water reservoir and further components of the dishwasher are avoided. To the contrary, the connections, like the fresh water reservoir itself, are protected by the housing of the dishwasher. Moreover the space requirement remains unchanged by comparison with a conventional dishwasher, so the dishwasher can be integrated without difficulty into a fitted kitchen having standard dimensions. Furthermore no interference in the design of the dishwasher is necessary.

According to a beneficial development of the invention the fresh water reservoir is therefore arranged between a possibly present housing and a washing compartment. Usually there are unused spaces in a dishwasher between its housing and the washing compartment. These are situated for example between a sidewall of the washing compartment and a sidewall of the housing, which run essentially in parallel. An easy-to-manufacture, flatly cuboid-shaped fresh water reservoir, for example, can be installed in a space of said kind. Thus it preferably has at most one cross-sectional width which corresponds to the width of the gap between the sidewall or back wall of the washing compartment and the outer housing. In addition the washing compartment is beneficially embodied to be sufficiently stable also to support a full fresh water reservoir. In this way it is possible to secure the fresh water reservoir directly to the washing compartment, thereby simplifying the construction of the dishwasher.

According to a particularly preferred development of the invention insulating means are provided which counteract a transfer of heat and/or a transmission of sound between washing compartment and fresh water reservoir. This can prevent the fresh water contained in the fresh water reservoir from drawing off a significant amount of heat from the washing compartment during a heating phase of a wash cycle, which would lead to a higher heating requirement. An improvement in the energy efficiency of the dishwasher can be realized in this way. Furthermore a lower level of noise transmission during the operation of the dishwasher can be achieved, which is beneficial in terms of comfort levels.

According to a beneficial development of the invention the fresh water reservoir is a plastic part, in particular made of polypropylene. Fresh water reservoirs of this type can be produced with little manufacturing overhead using, for example, suitable extruding or casting methods. Moreover storage containers manufactured from plastic exhibit a certain flexibility, with the result that their shape can adapt within certain limits to the available installation space. This factor enables a particularly efficient use of the available installation space.

According to a particularly preferred development of the invention the fresh water inlet device has a control valve, controllable by means of the control device, for filling the fresh water reservoir, the control valve being controlled in such a way that the fresh water reservoir is filled during and/or after termination of a wash program. By this means it is ensured that the fresh water reservoir is filled with fresh water during a pause or, as the case may be, in a residence interval between two wash programs, so that fresh water at room temperature or at least at close to room temperature will be available at the start of the subsequent wash program.

According to a beneficial development of the invention the control valve is controlled in such a way that the fresh water reservoir is filled during a final fresh-water-consuming wash subcycle of a wash program. In this way the time between introducing the fresh water into the fresh water reservoir and diverting the fresh water out of the fresh water reservoir can be maximized, with the result that the fresh water taken from the cold water supply at low temperature can also be heated to a significant degree even when two wash cycles are performed immediately after each other.

The final fresh-water-consuming wash subcycle of a wash program is usually a rinse cycle. If in this case the fresh water reservoir is filled immediately after the fresh water required for the rinse cycle is drawn off, the newly introduced fresh water can be heated already during the remaining time of the rinse cycle and during the following drying cycle, thereby increasing the efficiency of the dishwasher in particular when a further wash cycle is performed without a relatively long interval after the currently running wash cycle.

According to an advantageous development of the invention the control device is assigned a sensor for detecting the volume of fresh water contained in the fresh water reservoir. In this way introducing fresh water into the fresh water reservoir and/or drawing fresh water out of the fresh water reservoir can be controlled according to requirements.

According to a particularly preferred development of the inventive dishwasher the fresh water reservoir is embodied in such a way that fresh water can make its way into the washing compartment by virtue of its weight force via a controllable outlet. The controllable outlet can have, for example, an electrically actuatable valve that is controlled by the control device of the dishwasher. By this means it is easily possible to introduce fresh water contained in the fresh water reservoir into the washing compartment in a controlled manner. A conveying means, such as a pump, for example, is usually not required in this case.

According to an advantageous development of the invention the fresh water reservoir has an overflow which discharges into the washing compartment. In the event of a malfunction, for example a malfunction in the region of the fresh water inlet device or the outlet of the fresh water reservoir, this can prevent fresh water from leaking out of the dishwasher.

According to an advantageous development of the invention a free flow section can be assigned to the fresh water inlet device. The free flow section can be disposed in the fresh water reservoir for example. The purpose of the free flow section is to avoid a back-siphoning of fresh water in the direction of the cold water supply, which is inadmissible in particular on account of hygiene regulations, which back-siphoning could occur in the event of a temporary negative pressure arising in the cold water supply due to dynamic processes. In this way it is possible to avoid in particular too low a fresh water level in the fresh water reservoir.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention and its developments as well as their advantages are explained in more detail below with reference to drawings, in which:

FIG. 1 shows a schematized spatial representation of an exemplary embodiment of a dishwasher according to the invention;

FIG. 2 shows a block diagram of the dishwasher of FIG. 1;

FIG. 3 shows an advantageous functional diagram in order to illustrate the operation of a dishwasher according to the invention.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS OF THE PRESENT INVENTION

In the following figures parts corresponding to one another are labeled with the same reference signs. Only those components of a dishwasher that are necessary for understanding the invention are labeled with reference signs and explained therein. It is self-evident that the dishwasher according to the invention can comprise further parts and assemblies.

FIG. 1 shows a schematic spatial representation of an exemplary embodiment of a dishwasher 1 according to the invention. This has a washing compartment 2 which can be closed by means of a door 3 such that a washing cell for washing dishes is created. The washing compartment 2 is disposed in the interior of a housing 4 of the dishwasher 1 which has standard dimensions. Thus, for example, the housing 4 can have a width of 45 cm or 60 cm, thereby enabling the dishwasher 1 to be integrated into a standard type of fitted kitchen having a corresponding installation recess.

Disposed on the rear of the dishwasher 1 is a schematically represented fresh water inlet device 5. This has a fresh water connecting piece 6 to which a connecting hose 7 is connected. The connecting hose 7 is connected in the designated manner to an external cold water supply, in particular a cold water pipe, KH. In this case the connection is usually made to a cold water faucet KH provided in the building.

The dishwasher 1 according to the invention also has a fresh water reservoir 8. In this case the fresh water inlet device 5 comprises components (not shown in FIG. 1) which enable fresh water from the cold water faucet KH to be piped into the fresh water reservoir 8. The fresh water reservoir 8 is provided for the purpose of holding a reserve of fresh water available for a complete wash cycle for washing dishes. It enables the dishwasher 1 to accommodate the fresh water required for a complete wash cycle already before the wash cycle is performed. As a result thereof the fresh water which is provided by the cold water supply KH at a temperature in the range of, for example, 10° C. to 15° C. can be heated up to room temperature, which typically amounts to 20° C. to 25° in the room in which the dishwasher is installed, until it is needed for use as washing water. In this way the amount of energy required to bring the washing water to a designated washing temperature, which at least in phases during a wash cycle can amount to 50° C. or more, is reduced. The fresh water introduced into the fresh water reservoir can be brought to a temperature above its original supply temperature all the more through natural thermal energy exchange with the environment, in particular can assume the ambient temperature all the more readily, the longer the time it resides in the fresh water reservoir. After a sufficient waiting time following its introduction into the fresh water reservoir it therefore naturally assumes, through heat absorption from the environment of the installation site of the dishwasher alone, a feed-in temperature for feeding into the respective wash subcycle of the selected dishwashing program, which temperature is higher than its original supply temperature when it was introduced into the fresh water reservoir.

The fresh water reservoir 8 is disposed in the interior of the housing 4 of the dishwasher 1 such that the external dimensions of the dishwasher 1 according to the invention are no different from those of a conventional dishwasher. As a result it is possible without difficulty to integrate the dishwasher 1 according to the invention into a fitted kitchen having standard dimensions.

The fresh water reservoir 8 is preferably disposed in a space between a sidewall 9 of the washing compartment 2 and a sidewall 10 of the outer housing 4 of the dishwasher 1 running essentially parallel thereto, said space being unused in the case of a conventional dishwasher. The fresh water reservoir 8 is embodied as a very flat rectangular parallelepiped whose dimensions are adapted to the available installation space in order to enable this space to be utilized efficiently. It may also be possible to omit the outer housing 4. This can be beneficial in particular in the case of a built-in dishwasher which is e.g. integrated into an installation recess for a kitchen furniture unit.

Whereas the washing compartment 2 can be manufactured from stainless steel, the fresh water reservoir 8 is preferably made of plastic. The fresh water reservoir 8 can consist in particular of polypropylene, which is a low-cost and easily workable plastic. Thus, the fresh water reservoir 8 can be easily manufactured by means of extrusion or casting methods. In particular when the fresh water reservoir 8 is full, its material-related flexibility enables it to fit snugly against the sidewall 9 of the washing compartment 2 and the sidewall 10 of the housing 4. The available installation space is optimally used as a result, enabling a particularly large volume of fresh water to be stored. The fresh water reservoir 8 can in this case be secured by means not shown directly to the washing compartment 2, since the latter is usually sufficiently stable to take the weight of even a completely filled fresh water reservoir 8. In difficult space conditions it can also be provided that the fresh water reservoir 8 consists of a plurality of separate storage subunits which are disposed in different areas of the dishwasher 1 and are connected by means of tubes, pipes or the like.

In particular it can also be beneficial, according to an alternative construction, if the fresh water reservoir is mounted externally on the rear wall of the washing compartment 2.

A sump 11 is provided in a lower region of the washing compartment 2. A pump for circulating water in the washing compartment 2 during a wash cycle is provided in the sump 11. Also beneficially disposed in the sump 11 is a heater for heating the water contained in the washing compartment 2. A drain pump for pumping out water, at the end of a wash cycle for example, is likewise provided in the sump 11. However, the different pump functions can also be handled by means of a single pump in conjunction with switchable valves. The sump 11 is in this case connected to a drain connecting piece 12 via means not shown in such a way that water can be pumped out of the washing compartment 2 via a drain hose 13 connected to the drain connecting piece 12 into a waste water device A, for example a waste pipe A.

The dishwasher 1 additionally has a control device 14 in which at least one wash program for controlling an execution sequence of a wash cycle is stored. In the exemplary embodiment shown in FIG. 1 the control device 14 is disposed in the interior of the door 3 of the washing compartment 2. However, it could also be disposed at a different point on the dishwasher 1 such as e.g. in its base assembly underneath the washing compartment.

Various wash programs are beneficially stored in the control device 14; of these, one can be selected each time by an operator for the purpose of controlling a wash cycle. The wash programs can be different in terms of the cleaning effect they produce in order to be able to achieve an execution of a wash cycle that is geared to the degree of soiling of the items to be washed. In particular the number of wash subcycles provided here in each case for a wash program can be varied, which in many instances leads to the fresh water requirements for a wash cycle, i.e. the total volume of fresh water requiring to be fed in, being dependent on the wash program used in each case.

The fresh water reservoir 8 has a storage capacity sized such that the fresh water requirements for all the wash subcycles of at least one of the wash programs can be covered by the fresh water that can be stored in the fresh water reservoir 8. In this way the amount of energy required for heating the washing water during the performance of a wash cycle on the basis of said wash program is reduced, thereby improving the energy efficiency of the dishwasher 1. A further improvement in energy efficiency can be achieved when the storage capacity of the fresh water reservoir 8 is dimensioned such that the fresh water requirements of a plurality of or of all of the wash programs can be covered by the fresh water that can be stored in the fresh water reservoir 8.

The storage capacity of the fresh water reservoir 8 can amount, for example, to at least 8 liters, which can be adequate for a wash program for lightly soiled dishes. Preferably the storage capacity amounts to at least 12 liters, which in the case of a dishwasher 1 can also be sufficient for a wash program for cleaning normally soiled dishes. Particularly preferably the storage capacity amounts to at least 16 liters, which usually will also cover the total fresh water requirements for a wash program for heavily soiled dishes.

FIG. 2 shows a block diagram of the dishwasher shown in FIG. 1. The fresh water inlet device 5 includes a control valve 15 which can be controlled by means of the control device 14. The control valve 15 of the fresh water inlet device 5 is disposed downstream of the fresh water connecting piece 6. In this way the inflow of fresh water into the fresh water reservoir 8 can be controlled by the control device 14. The energy required for filling the fresh water reservoir 8 is usually provided by the pressure prevailing in the cold water supply, in particular a cold water pipe, with no pump or similar being required in these cases for filling the fresh water reservoir 8.

A free flow section 16 is provided downstream of the control valve 15. The free flow section 16 is what is referred to as a pipe interrupter, which serves to prevent an impermissible (in particular for hygiene reasons) back-siphoning of water from the dishwasher 1 if a negative pressure is created in the external cold water supply due to dynamic processes. In particular this prevents fresh water already heated to room temperature being sucked out of the fresh water reservoir 8 and back into the cold water supply when a dishwasher is switched off, which could result in not enough fresh water heated to room temperature being available during a subsequent execution of a wash cycle and then colder fresh water needing to be used.

Disposed at the lower end of the fresh water reservoir 8 is a controllable outlet 17 which discharges into the washing compartment 2. The controllable outlet 17 includes a control valve 18 which can also be controlled by means of the control device 14. When the control valve 18 is opened, fresh water flows by virtue of its weight force into the washing compartment 2. In this way it is possible even without a pump or the like to direct fresh water contained in the fresh water reservoir 8 into the washing compartment 2 as a function of the selected wash program.

In order to prevent fresh water leaking out of the dishwasher 1 in the event of a malfunction, a malfunction of the control valve 18 for example, the fresh water reservoir 8 is assigned an overflow 19 which discharges into the washing compartment 2.

The control device 14 is connected to a sensor 21 for detecting the volume of fresh water contained in the fresh water reservoir 8. This enables in particular a precise control of the control valve 15 of the fresh water inlet device 5 when receiving fresh water from the cold water supply in order thus to be able to set a desired fill level exactly. However, the signals of the sensor 21 can also be used for controlling the control valve 18 of the outlet 17 in order to enable fresh water to be dispensed from the fresh water reservoir 8 in a precisely metered fashion.

Arranged between the fresh water reservoir 8 and the washing compartment 2 is a layer-like insulating means 22 which reduces heat transfer and/or sound transmission between washing compartment 2 and fresh water reservoir 8. On the one hand this prevents the fresh water contained in the fresh water reservoir 8 from drawing off a significant amount of heat from the washing compartment 2 during a heating phase of a wash cycle, which would lead to a higher heating requirement. An improvement in the energy efficiency of the dishwasher can be achieved in this way. On the other hand, however, it enables noise transmission during the operation of the dishwasher to be reduced, which is beneficial in terms of comfort levels.

The one or more electrical components disposed in the sump 11 are controlled by means of the control device 14. Thus, washing water contained in the washing compartment 2 can be selectively heated, circulated via a spray device 20 and pumped away to the outside via the drain connecting piece 12.

FIG. 3 illustrates an advantageous mode of operation of a dishwasher embodied in accordance with the inventive construction principle. FIG. 3 shows the curves MFW and TFW on a common time axis t. Here, the curve MFW represents the volume MFW of fresh water which is stored in the fresh water reservoir at a specific time. The volume of fresh water is in this case specified relative to the maximum storable volume, i.e. relative to the storage capacity of the fresh water reservoir. In this case the value 100% means that the fresh water reservoir is filled to a maximum, while the value 0% means that the fresh water reservoir is completely empty. The storage capacity can equal 15 liters, for example. The curve TFW represents the temperature TFW of the water contained in the fresh water reservoir 2.

FIG. 3 shows an end phase of a first wash cycle SG1 and a second, subsequent wash cycle SG2 that is separated in time from the first wash cycle by means of an interval. The wash cycles SG1 and SG2 are in each case performed automatically on the basis of a wash program selected by the operator. As wash subcycles, the respective wash program provides, in chronological order, a prewash cycle VG, a cleaning cycle RG, an intermediate wash cycle ZG, a rinse cycle KG and a drying cycle TG. In this case the control device controls all the components of the dishwasher each time, in particular the control valve 15 of the fresh water inlet device shown in FIG. 2 and, also shown in FIG. 2, the control valve 18 of the outlet 17 of the fresh water reservoir 8. It is self-evident that the advantages according to the invention can also be achieved in the case of other, modified wash programs. Thus, for example, a wash program would be possible which dispenses with the prewash cycle VG and/or the intermediate wash cycle ZG. A wash program in which a plurality of cleaning cycles are provided would also be possible.

At the start of the rinse cycle KG of the first, earlier wash cycle SG1 the fresh water reservoir is still approximately 40% full. In this case the temperature TFW of the fresh water in the fresh water reservoir essentially corresponds to the ambient temperature of the dishwasher, i.e. a room temperature TR of, for example, 22° C. Immediately after the start of the rinse cycle KG a volume of fresh water required for performing the rinse cycle KG is extracted from the fresh water reservoir. This can amount, for example, to 20% of the storable volume or 3 liters.

The rinse cycle KG is the last wash subcycle of the wash cycle SG1 that requires fresh water. Therefore the fresh water reservoir is completely filled immediately after the fresh water is extracted for the rinse cycle in order to maximize the time interval between the filling of the fresh water reservoir with fresh water and the extracting of fresh water in a following wash cycle SG2. In this way the fresh water supplied at the temperature TK of the cold water supply, which equals 14° C. for example, can be heated to a maximum extent up to the time of its being drawn off, in particular to a feed-in temperature for feeding into the washing compartment, which temperature is higher than its original inflow temperature into the fresh water reservoir. In this case it can even be higher than the ambient temperature or, as the case may be, room temperature, since during the rinsing process the water used therein is heated so far above room temperature that a perfect drying result can be achieved for cleaned items to be washed that now require drying, owing to what is known as sensible heat convection of the heated items to be washed and condensate formation on the walls of the washing compartment which are colder by comparison with the items being washed. This choice of the feed-in time for introducing fresh water into the fresh water reservoir is of advantage in particular when the time between the end of the first wash cycle SG1 and the end of the second wash cycle SG2 is limited. However, exemplary embodiments are also conceivable in which the fresh water reservoir is filled at a later time, for example during or following a concluding drying cycle TG of the wash cycle SG1.

In the example shown in FIG. 3 the fresh water supplied from the cold water supply and the remaining fresh water contained in the fresh water reservoir are mixed roughly in a ratio of 4 to 1. This causes the temperature TFW in the fresh water reservoir to drop sharply, though it is still above the temperature TK of the cold water source. In this case a temperature of, for example, 16° C. is established. Starting from this value the temperature TFW in the fresh water reservoir increases during the remaining time of the rinse cycle KG and during the following drying cycle TG on account of the higher ambient temperature TR. At the end of the drying cycle TG, during which no fresh water is drawn off from the fresh water reservoir, the temperature TFW in the fresh water reservoir can already amount to 19° C., for example.

The temperature TFW continues to increase after completion of the wash cycle SG1 and up to the start of a following wash cycle SG2. If there is a relatively long interval between the wash cycles SG1 and SG2, as happens very often in practice, the temperature TFW in the fresh water reservoir at the start of the second wash cycle SG2 has essentially reached room temperature TR or may even lie above it. This means that if, as in the exemplary embodiment of FIG. 3, a corresponding storage capacity of the fresh water reservoir is provided, fresh water at least at room temperature TR, which is significantly above the temperature TK of the cold water supply, is available at the start of each fresh-water-consuming wash subcycle VG, RG, ZG and KG of the wash cycle SG2. In this case approximately 20% of the capacity of the fresh water reservoir is drawn off from the latter each time at the start of one of the wash subcycles VG, RG, ZG and KG.

In this way a higher washing temperature than the original cold water temperature is produced for the unheated water-conducting wash subcycles, i.e. for the prewash cycle VG and the intermediate wash cycle ZG for example, thereby increasing the cleaning effect of said wash subcycles while the energy requirement effectively remains the same. In the heated water-conducting wash subcycles, i.e. during the cleaning cycle RG and during the rinse cycle KG for example, the result is an energy saving, which is due to the fact that in the case of the preheated fresh water less heat needs to be supplied in order to reach the washing temperature provided for the respective wash subcycle. Because of the higher average temperature during the wash cycle using water that has been preheated by the ambient heat at the installation site of the dishwasher and/or by means of one or more heating processes of one or more wash subcycles of an earlier, preceding wash cycle, a higher thermal cleaning effect is produced in addition. As a result it is possible in many cases to shorten the designated running time of a wash program, which can lead not only to a time saving, but also to an energy saving e.g. owing to a shorter operating time of the circulating pump.

In the example shown in FIG. 3, approximately 20% of the total storable volume of fresh water is taken each time from the fresh water reservoir at the start of one of the wash subcycles VG, RG, ZG and KG of the wash cycle SG2. In a wash cycle SG2 of said type approximately 20% of the maximum volume therefore remains in the fresh water reservoir at all times. Such a dimensioning of the storage capacity of the fresh water reservoir enables the total fresh water requirements to be covered from the fresh water reservoir even for a wash cycle that is controlled in accordance with a further wash program which provides an additional second cleaning cycle, which, for example, also allows a wash cycle for more heavily soiled dishes to be performed efficiently.

To sum up, it can be noted that in the case of an advantageously embodied dishwasher the fresh water for at least two wash subcycles such as e.g. cleaning and rinsing, in particular for an entire wash cycle, i.e. for all the wash subcycles of a dishwashing program, can be held available in reserve in a tank or fresh water reservoir. In this arrangement the fresh water can assume the ambient temperature of the room in which the dishwasher is installed, in particular of the kitchen, through simple transfer of heat from the environment, i.e. preferably without further auxiliary heating, with the result for example that a feed-in temperature such as e.g. 23° C. can be produced for the (unheated) washing liquor, which temperature is in many cases higher than the temperature at which the fresh water is drawn off from a cold water pipe, which amounts to 15° C., for example. The energy that is additionally required in order to reach a specific process temperature of the washing liquor in the respective wash subcycle of the selected dishwashing program can therefore be lower than in the case without fresh water reservoir. An energy saving is therefore made possible.

It can be particularly beneficial to perform the filling process of the fresh water reservoir during and/or immediately after termination of the wash cycle of a selected dishwashing program, in particular its final wash subcycle, with an additional heating process such as e.g. rinsing process and/or following drying process, so that the stored fresh water can absorb as much thermal energy as possible from the interior of the washing compartment. This has the advantage that a relatively short time during which the fresh water resides in the fresh water reservoir can already be sufficient to enable it to be brought to a higher temperature compared to its original feed-in temperature. In this way fresh water preheated by said means can also be used for a dishwashing program started immediately following, without it being necessary to wait for a minimum waiting time to elapse, as would normally be required in order for the temperature of the fresh water in the fresh water reservoir to adjust to the ambient temperature in the event of non-utilization of the waste heat from the interior of the washing compartment. 

1. A dishwasher, comprising: a control device to call at least one wash program for controlling a wash cycle for washing items to be washed; a fresh water inlet device to receive fresh water from an external cold water supply; a fresh water reservoir to be filled with fresh water by means of the fresh water inlet device, wherein a first predetermined volume of the fresh water is stored in the fresh water reservoir that is sufficient to cover a first fresh water requirement of the wash cycle in the at least one wash program.
 2. The dishwasher of claim 1, wherein the dishwasher is a domestic dishwasher.
 3. The dishwasher of claim 1, wherein a second predetermined volume of the fresh water is stored in the fresh water reservoir that is sufficient to cover a second fresh water requirement of the wash cycle of one of a plurality of wash programs.
 4. The dishwasher of claim 1, wherein a third predetermined volume of the fresh water is stored in the fresh water reservoir that is sufficient to cover a third fresh water requirement of the wash cycle for each of the at least one wash program.
 5. The dishwasher of claim 1, wherein at least 8 liters of the fresh water are stored in the fresh water reservoir.
 6. The dishwasher of claim 1, wherein at least 12 liters of the fresh water are stored in the fresh water reservoir.
 7. The dishwasher of claim 1, wherein at least 16 liters of the fresh water are stored in the fresh water reservoir.
 8. The dishwasher of claim 1, further comprising a washing compartment having at least one wall, wherein the fresh water reservoir is disposed externally on the at least one wall of the washing compartment.
 9. The dishwasher of claim 1, further comprising an outer housing and an internally disposed washing compartment, wherein the fresh water reservoir is disposed in an interspace between the outer housing and the internally disposed washing compartment.
 10. The dishwasher of claim 1, further comprising a washing compartment and insulating means, the insulating means to counteract at least one of a transfer of heat and a transmission of sound between the washing compartment and the fresh water reservoir.
 11. The dishwasher of claim 1, wherein the fresh water reservoir is a plastic part.
 12. The dishwasher of claim 11, wherein the plastic part is made of polypropylene.
 13. The dishwasher of claim 1, wherein the fresh water inlet device has a control valve that is controlled by means of the control device so as to fill the fresh water reservoir, and wherein the control valve is controlled such that the fresh water reservoir is filled at least one of during and after termination of the wash cycle.
 14. The dishwasher of claim 13, wherein the control valve is controlled such that the fresh water reservoir is filled during a final fresh-water-consuming wash subcycle of the wash cycle.
 15. The dishwasher of claim 1, further comprising a sensor that is assigned to the control device, the sensor to detect an actual volume of the fresh water contained in the fresh water reservoir.
 16. The dishwasher of claim 1, further comprising a washing compartment and a controllable outlet, wherein the fresh water reservoir is structured such that the fresh water reaches the washing compartment through a weight force of the fresh water via the controllable outlet.
 17. The dishwasher of claim 1, further comprising a washing compartment, wherein the fresh water reservoir has an overflow that discharges into the washing compartment.
 18. The dishwasher of claim 1, further comprising a free flow section that is assigned to the fresh water inlet device.
 19. The dishwasher of claim 1, wherein at least one of raw water from a cold water source, treated process water or gray water from a water treatment plant, cistern water from a cistern plant, well water from a well pumping system, and water from another type of cold water provisioning device is used as the fresh water of the cold water supply.
 20. The dishwasher of claim 1, wherein a fourth predetermined volume of the fresh water stored in the fresh water reservoir corresponds at least to a total water volume required for complete performance of all wash subcycles of a respective one of the at least one wash program.
 21. The dishwasher of claim 1, wherein the wash cycle of the at least one wash program has at least two wash subcycles.
 22. The dishwasher of claim 21, wherein the at least two wash subcycles include cleaning and rinsing. 